Simple plumbing question re: teflon tape

[kenmac]

Seems to defeat the whole point and purpose of using threaded fittings in the first place, doesn't it? would such a system still meet the plumbing code? are malleable or cast iron fittings still good if back welded?

Theo

This would have to be SS pipe & fittings or, steel pipe & fittings. No threads & no cast iron fittings